1. Field of the Invention
The present invention relates to an electrical-wire support apparatus.
2. Description of the Related Art
Conventionally, in electronic devices, such as personal computers, cellular phones, personal digital assistants (PDAs), digital cameras, video cameras, music players, game machines, and vehicle navigation devices, a casing is designed to be foldable so as to reduce the overall size of the casing and simultaneously increase the size of a display (see, for example, Japanese Patent Application Laid-Open (kokai) No. 2003-258961).
FIG. 9 is a view showing wiring for connecting boards in a conventional foldable electronic device.
In FIG. 9, a first circuit board 301 is mounted on a first casing of a cellular mobile telephone, which is an example foldable electronic device. A second circuit board 302 is mounted on a second casing rotatably attached to the first casing.
A flexible wiring board or flexible printed circuit 303 serves as an electrical wire for connecting the first circuit board 301 and the second circuit board 302. A first wiring connector 304 attached to one end of the flexible wiring board 303 is connected to a first board mount connector 305 mounted on the first circuit board 301. A second wiring connector 306 attached to the other end of the flexible wiring board 303 is connected to a second board mount connector 307 mounted on the second circuit board 302.
An intermediate portion of the flexible wiring board 303 is wound around a cylindrical fixation tube 308 having a longitudinal slit, and is supported thereby. The fixation tube 308, which serves as an electrical-wire support apparatus, is disposed within a hinge portion that provides rotatable connection between the first and second casings. This configuration enables the first casing to be rotated in relation to the second casing about an axis shown by arrow A. Therefore, even when the first casing is rotated in relation to the second casing as a result of an operation of opening a display portion of the cellular phone in the folded state so as to make a call, the flexible wiring board 303, which serves as electrical wires, can smoothly deform, so that the first and second circuit boards 301 and 302 can maintain electrical connection therebetween.
However, the above-described conventional electrical wire support apparatus can cope with only rotations motion about a single axis, and cannot cope with rotational motions about two axes. Therefore, the conventional electrical-wire support apparatus cannot cope with a complex connection between two or more casings. Recently, electronic devices, such as cellular phones, are designed such that, in order to improve the visibility of a display, one casing supporting the display can be rotated about an axis to open in relation to the other casing, and can be further rotated about another axis. By virtue of this structure, a user of the electronic device can freely change the orientation of the display. The electrical-wire support apparatus shown in FIG. 9 cannot cope with such rotation about two axes. Specifically, even in the case where a hinge portion which enables rotation about an axis perpendicular to the axis indicated by arrow A is employed, if the display is rotated about the axis perpendicular to the axis indicated by arrow A, the flexible wiring board 303 is twisted, which makes the rotation about two axes difficult. Use of a cable composed of a plurality of electrical wires in place of the flexible wiring board 303 enables rotation about two axes, because the cable allows some degree of twist. However, in this case, if the cable is twisted, force acts on neck portions of the cable; i.e., opposite end portions of the cable connected to the wiring connectors, whereby the wires of the cable may be broken, or signals transmitted therethrough may suffer disturbance.